A conventional pin lock or coupler lock lockably secures a lock housing to an end of a shaft, such that the shaft may be securely retained through one or more apertures, for example, to secure two or more apertured members together. As one example, a pin lock may lockably secure a trailer hitch within a receiver tube by inserting the shaft of the pin lock through aligned holes in the receiver tube and trailer hitch, and then locking the lock housing to the end of the shaft. The lock housing and an enlarged head on the opposite end of the shaft prevent withdrawal of the shaft in either direction.